What is the equivalent of the C# 'var' keyword in Java?

The reason C# has the var keyword is because it's possible to have Types that have no name in .NET. Eg:

var myData = new { a = 1, b = "2" };

In this case, it would be impossible to give a proper type to myData . 6 years ago, this was impossible in Java (all Types had names, even if they were extremely verbose and unweildy). I do not know if this has changed in the mean time.

var is not the same as dynamic . var iables are still 100% statically typed. This will not compile:

var myString = "foo";
myString = 3;

var is also useful when the type is obvious from context. For example:

var currentUser = User.GetCurrent();

I can say that in any code that I am responsible for, currentUser has a User or derived class in it. Obviously, if your implementation of User.GetCurrent return an int, then maybe this is a detriment to you.

This has nothing to do with var , but if you have weird inheritance hierarchies where you shadow methods with other methods (eg new public void DoAThing() ), don't forget that non-virtual methods are affected by the Type they are cast as.

I can't imagine a real world scenario where this is indicative of good design, but this may not work as you expect:

class Foo {
    public void Non() {}
    public virtual void Virt() {}
}

class Bar : Foo {
    public new void Non() {}
    public override void Virt() {}
}

class Baz {
    public static Foo GetFoo() {
        return new Bar();
    }
}

var foo = Baz.GetFoo();
foo.Non();  // <- Foo.Non, not Bar.Non
foo.Virt(); // <- Bar.Virt

var bar = (Bar)foo;
bar.Non();  // <- Bar.Non, not Foo.Non
bar.Virt(); // <- Still Bar.Virt

As indicated, virtual methods are not affected by this.

No, there is no non-clumsy way to initialize a var without an actual variable.

var foo1 = "bar";        //good
var foo2;                //bad, what type?
var foo3 = null;         //bad, null doesn't have a type
var foo4 = default(var); //what?
var foo5 = (object)null; //legal, but go home, you're drunk

In this case, just do it the old fashioned way:

object foo6;